The present invention relates to a container comprising a squeezing pressure source, which acts upon creamy or liquid media, a discharge valve element for these media, as well as an appliance, which is able to keep the loss of squeezing pressure inevitably caused by stress and storage aging as low as possible and which allows to empty the container entirely except for the valve ducts.
Several patents, e.g. the U.S. Pat. No. 566,282, the U.S. Pat. No. 821,875, the U.S. Pat. No. 2,738,227, the U.S. Pat. No. 3,672,543 and the U.S. Pat. No. 3,796,356 describe spraying appliances relating to different embodiments in which macromolecular materials of the caoutchouc type are used as a pressure source. Non of these patents does in any way whatsoever mention a means to influence an inevitable loss of pressure due to the permanent loss of elasticity in the caoutchouc used.
The applicant of the Swiss Pat. No. 618 355 is the first who describes therein a rigid inner core, which is enveloped by a rubber hose serving as pressure source and having an inner diameter that is by preferably 75 percent larger than the inner diameter of the unstressed rubber hose, whereby a permanent extension of the inner diameter of the hose caused by stress and aging is avoided which would lead to a product loss through a loss of stress.
This solution proposed by the applicant represents a substantial progress as far as the use of the contractional force of an expanded rubber hose is concerned, but it can in no way influence the inevitable loss of contractional force caused by permanent stress and aging of the rubber used.
Examinations having been carried out for more than five years on the behavior of a radially-axially expanded rubber hose have shown that in addition to a permanent expansion a loss of contractional force is observed, which increases with the square proportionally to the percentage of expansion.
If such a rubber hose as described in the Swiss Pat. No. 618 355 by the applicant is used for gas-free spraying cans the loss of contractional force limits the use of such spraying cans to products only where the particle size of the sprayed product and the discharge rate per second is not important, as well as to products that do not have to be sprayed at all like oils, creams, etc.; in the latter case, however, their viscosity has to be so small that they can be discharged despite the loss of contractional force of the rubber hose, which serves as squeezing pressure source.
It is possible to decrease the loss of contractional force in limiting the expansion percentage of 450, as described in the Swiss Pat. No. 618,355, to 225 percent and in admixing preferably CO.sub.2 or other inert gases to the product, as suggested by the applicant in the European Patent Application No. 80901498.8.
In this proposed solution the contraction pressure of the rubber hose prevents the escape of CO.sub.2 from the product solution on the filling day. But as soon as the contraction pressure drops below the pressure level at which CO.sub.2 escapes from the product solution, a CO.sub.2 -gas bubble is formed, the pressure of which acts on the product surface. Since the rubber hose contracts during discharge, i.e. the residual volume between the gas bubble and the product level remains equal, the CO.sub.2 -pressure acting on the product surface remains equal, too. However, this solution requires that such a spraying can has always to be used in a vertical position, otherwise CO.sub.2 will escape which then leads to a pressure loss. Moreover this system is very susceptible to temperature. At temperatures over 30.degree. C. such a big CO.sub.2 -gas bubble may form as to cause the bursting of the rubber hose. On the other hand temperatures below 10.degree. C. may hamper the escape of CO.sub.2 from the product so that the compensation of the contraction loss in the rubber hose aimed at is not achieved. Furthermore shaking may cause the dissolution of CO.sub.2 from the product to such an extent that the large CO.sub.2 -gas bubble formed this way may cause the bursting of the system.